Preheat your oven to the temperature indicated on the cake mix box.
In a mixing bowl, combine the sugar-free cake mix, fat-free Cool Whip, and one egg.
Mix the ingredients until well combined. The dough will be quite sticky, so you can refrigerate it for about 15-30 minutes to make it easier to handle.
Use a spoon to drop small portions of the dough onto a parchment-lined baking sheet, leaving enough space between each cookie as they will spread while baking.
Bake the cookies in the preheated oven for the time specified on the cake mix box or until they are lightly browned and set.
Allow the cookies to cool on a wire rack before serving.